Power module substrate and power module

Abstract

A power module substrate includes an insulating substrate and a metal plate. The metal plate is joined to the insulating substrate with a brazing material in between. As to surface roughness of a lateral surface of the metal plate in a thickness direction, the surface roughness of at least a corner part farthest from a center of the metal plate in plan view is larger than the surface roughness of plane parts sandwiching the corner part.

The invention claimed is: 
     
       1. A power module substrate comprising:
 an insulating substrate; and 
 a metal plate joined to the insulating substrate with a brazing material in between, wherein
 a lateral surface of the metal plate includes corner parts and plane parts, the plane parts sandwiching a corner part of the corner parts, and 
 at least at the corner part farthest from a center of the metal plate in plan view, a surface roughness of the lateral surface of the metal plate is larger than the surface roughness at the plane parts sandwiching the corner part. 
 
 
     
     
       2. The power module substrate according to  claim 1 , wherein the surface roughness gradually increases from the plane parts to the corner part. 
     
     
       3. The power module substrate according to  claim 1 , wherein the corner part is convex in plan view. 
     
     
       4. A power module comprising:
 the power module substrate according to  claim 1 , and 
 an electronic component mounted on the metal plate of the power module substrate. 
 
     
     
       5. The power module substrate according to  claim 2 , wherein the corner part is convex in plan view. 
     
     
       6. A power module comprising:
 the power module substrate according to  claim 2 ; and 
 an electronic component mounted on the metal plate of the power module substrate. 
 
     
     
       7. A power module comprising:
 the power module substrate according to  claim 3 ; and 
 an electronic component mounted on the metal plate of the power module substrate. 
 
     
     
       8. The power module substrate according to  claim 1 , further comprising
 two small metal plates, and 
 wherein the two small metal plates are smaller than the metal plate. 
 
     
     
       9. The power module substrate according to  claim 8 , wherein
 the two small metal plates are arranged such that the metal plate is between the two small metal plates on the insulating substrate. 
 
     
     
       10. The power module substrate according to  claim 1 , wherein on a diagonal, a pair of quadrangular corners of the metal plate are notched. 
     
     
       11. The power module substrate according to  claim 10 , further comprising
 two small metal plates, and 
 wherein the two small metal plates are arranged in the notch of the pair of quadrangular corners of the metal plate. 
 
     
     
       12. The power module substrate according to  claim 3 , wherein a radius of the corner part is 0.1 to 3 mm in plan view. 
     
     
       13. The power module substrate according to  claim 1 , wherein the surface roughness at the plane parts of the lateral surface is 0.3 μm to 1.0 μm, the surface roughness being arithmetic mean roughness Ra. 
     
     
       14. The power module substrate according to  claim 1 , wherein the surface roughness at the corner part of the lateral surface is 0.5 μm to 1.5 μm, the surface roughness being arithmetic mean roughness Ra. 
     
     
       15. The power module substrate according to  claim 1 , further comprises
 a meniscus-shaped fillet part between the lateral surface and an upper surface of the insulating substrate formed by the brazing material. 
 
     
     
       16. The power module substrate according to  claim 1 , wherein in a thickness direction, the surface roughness of the lateral surface of the metal plate at the corner part is larger than the surface roughness at the plane parts sandwiching the corner part.